Water treatment methods



Nov.

Raw Wafer E. s. STODDARD 2,912,372

WATER TREATMENT METHODS Original Filed May 12. 1955 24 o 2% 2. a a 3 38.33 39 35 Base So/uf/on g; I 21 36 57 59 -0 5&8 f o c Haw Wafer INVENTOR.

EdgarS Sfoddard WATER TREATMENT METHODS Edgar S. Stoddard, Berwyn, 113.,assignor to General Electric Company, a corporation of New York 9Claims. (Cl. 204-151) The present invention relates to water treatmentmethods, and more particularly to such methods that are especiallydesigned to convert raw water containing dissolved mineral salts intocorresponding aqueous acid and base solutions. This application is adivision of the copending application of Edgar S. Stoddard, Serial No.

507,805, filed May 12, 1955, now Patent No. 2,825,666, granted March 4,1958.

It is the general object of the invention to provide an improved methodof treating ordinary hard water for the purpose of producing separateand distinct aqueous acid and base solutions therefrom.

Another object of the invention is to provide a water treatment methodthat involves simultaneous ion exchange and electrodialysis steps.

A further object of the invention is to provide a water treatment methodin which there is produced separate aqueous acid and base solutions in aready and simple manner from ordinary hard water without attention onthe part of the operator, whereby the method may be carried out in adishwasher or other home appliance.

Further features of the invention pertain to the particular arrangementof the steps of the method, whereby the above-outlined and additionaloperating features thereof are attained.

The invention, both as to its organization and method of operation,together with further objects and advantages thereof, will best beunderstood by reference to the following specification taken inconnection with the accompanying drawing, in which the single figure isa vertical sectional view of a water treatment unit in which the methodof the present invention may be carried out.

Referring to the drawing, the water treatment unit 10 there illustrated,comprises an upstanding substantially cylindrical outer tubular casing11 formed of stainless steel and constituting a cathode, an upstandingsubstantially rod-like member 12 formed of carbon and con-- stitutingananode, and an upstanding substantially cylindrical tubular permeablediaphragm or barrier 13 formed of ceramic material and arranged ininterposed-relation with respect to the anode 11 and the anode 12 andconcentric therewith. The lower end of the cathode 1 1 is provided withaninwardly directed annular flange 14 and the upper end of the cathode11 is provided with an outwardly directed annular flange 15; andpreferably the anode 12 is arranged along the longitudinal axis of theunit. Thus the cathode 11 cooperates with the barrier 13 to define asubstantially annular cathode chamber 16 therebetween, and the anode 12cooperates with the barrier 13 to define a substantially annular anodechamber 17 therebetween;

The opposite lower and upper ends of the cathode 11 are closed by a pairof longitudinally spaced-apart substantially disk-like insulating plates18 and 19. The lower plate 18 is supported upon thelower flange 14 withan annular sealing gasket 20 arranged therebetween; and the, upper plate19 is secured in place by an associated clamping ring 21 disposedthereabove, an annular Sealing gasket 22 being arranged mutually betweenthe United States Patent '0 ice 'upperplate 19, the clamping ring '21and the adjacent upper endwall of the cathode 11. More particularly, thebarrier 13 is clamped in position between the plates 18 and 19 by thearrangement including the clamping ring 21, the upper face of'the lowerplate 18 having an annular groove 23 therein receiving the adjacentlower end of the barrier 13, and the lower face of the upper plate 19having an annular groove 24 therein receiving the adjacent upper end ofthe barrier 13. In the arrangement, two sealing gaskets 25 and 26 arerespectively arranged in the grooves 23 and 24 and respectively engagethe lower and upper ends of the barrier 13, thereby to 7 form aliquid-tight seal between the cathode chamber 16- and the anode chamber17. The clamping ring 21 may be secured in place to the adjacent annularflange 15' therebelow by a plurality of screws 27 provided with as--sociated nuts 28 in order to complete the assembly. .In the arrangement,the plates 18 and 19 may be formed of phenol-formaldehyde condensationproducts; the gaskets 20, 22, 25 and 26 may be formed of neoprene; andthe clamping ring 21 may be formed of any suitable material.

The anode 12 extends through longitudinally spacedapart and alignedopenings formed in the central portions of the plates 18 and 19; andpreferably the major portion of the anode 12 is jacketed by a tubularsleeve 29 of insulating material. The upper portion of the sleeve 29extending through the central opening provided in the upper plate 19 tothe exterior of the anode chamber 17 is imperforate and suitablycemented in liquid-tight relation to the adjacent upper portion of theanode 12, as indicated at 30; while the lower portion of the sleeve 29extending into the anode chamber 17 is perforated, as indicated at 31,to accommodate contact of the anode 12 by the anolyte in the anodechamber 17. The extreme lower end of the anode 12 is positioned in thecentral opening provided in the lower plate 18 by an interveningsubstantially cup-shaped supporting member 32. In the arrangement, thesleeve 29 and the cup 32 may be formed of phenol-formaldehydecondensation products. Also an ion exchange bed, indicated at 33, isarranged within the barrier 13 and embedding the anode 12. In

' spaced somewhat below the upper plate 19' by an inter posed spacingringz38 to define an annular chamber 39 therebetween. In thearrangement, the plates 34 and 35,

p as well'as the spacing rings 36 and 38, may be formed ofphenol-formaldehyde condensation products. Preferably, the porous bed 33completely fills the space within the anode chamber 17 defined mutuallybetween the sleeve 29 and the barrier 13 and the upper and lower plates34 and 35; the holes provided in the plates 34 and 35 are of the samesize in order to prevent pressure differentials between the chambers 39,17 and 37 when the anolyte is passing in a stream through the anodechamberf17, the holes provided in the plates 34 and 35 beingsufficiently small to prevent the excape of the individual particles ofthe porous bed 33 from the anode chamber 17 The outer ends of thecentral openings formed in the plates 18 and 19are threaded andrespectively receive the threaded ends of lower and upper tubularelements 40: and 41 respectively arranged in liquid-tight relationtherewith. An annular array of holes 42 is provided in the lower plate18 and communicating between the upper end of the tubular element 40 andthe annular chamber 37; and likewise, an annular array of holes 43 isprovided in the upper plate 19 and communicating between the lower endof the tubular element 41 and the annular chamber 39. The extreme lowerend of the tubular member 40 is threaded in order to receive any desiredconnecting fitting; and likewise, the extreme upper end of the tubularmember 4-1 is threaded and carries a substantially T-shaped fitting 44having a longitudinally extending hollow head 45 surrounding the anode12 and a laterally extending stem 46 receiving the threaded inner end ofa tubular member 47, the outer end of the tubular member 47 beingthreaded to receive any desired con necting fitting. The upper end ofthe head 45 is threaded :and receives the lower end of a longitudinallyextending tubular member also surrounding the anode 12. The upper end ofthe tubular member 48 is threaded and receives an inverted substantiallycup-shaped fitting 49 also surrounding the anode 12. A substantiallysleevelike compressible sealing gasket Sill, that may be formed ofneoprene, is arranged within the upper end of the tubular member 43 andwithin the fitting 49 in surrounding relation with the sleeve 29 andretained in compression by the fitting 49 in order to provide aliquid-tight joint or gland closing the upper end of the tubular member48 and sealing the same with respect to the exterior. The extreme upperend of the sleeve 29 and the anode 12 project through a central opening51 provided in the fitting 59 to the exterior; and the extreme upper endof the anode 22 projects beyond the extreme upper end of the sleeve 29and carries a terminal strap or fixture 52 that is adapted to beconnected to the ungrounded positive terminal of a direct current sourceof supply. Also a terminal strap 53 is secured to the cathode 11 andadapted to be connected to the grounded negative terminal of the directcurrent source of supply mentioned.

Further, the unit it is provided with a flow control device that maytake the form of a plug 54 arranged in the outer end of the tubularmember 47 and having a centrally disposed opening 55 formedtherethrough; the body of the plug 54 being formed of resilientmaterial, such, for example, as neoprene, or the like, so that theconfiguration thereof may be somewhat distorted in response to anabnormal pressure in the associated inlet supply connection, not shown,so as to reduce the efiective cross-sectional area of the hole 55therethrough with the contracting flow-regulating effect with respect tothe passage of water into the fitting 44. In other Words, the flowcontrol plug 54 is designed to accommodate the passage through. the hole55 of a substantially fixed flow of water when the tubular member 47 isconnected to household plumbing involving the usual water pressuresencountered therein, a conventional manually operable valve 56 beingarranged in the plumbing connection mentioned preceding the tubularmember 47. Two conduits 57 and '8 are respectively secured inliquid-tight relation with lower and upper openings provided in the wallof the cathode 1i and communicating with the respective lower and upperends of the cathode chamber 16, the conduit 57 being connected to thehousehold plumbing and including a manually operable valve 5%. Thetubular element 4* is connected to upstanding conduit structure 6i? towhich the acid solution is supplied from the anode chamber 17; and theconduit 53 is connected to conduit structure 61 to which the basesolution is supplied from the cathode chamber 16. In the arrangement,the conduit structure 60 is disposed in upstanding relation and extendsabove the anode chamber 17 so as to insure that the porous ion exchangebed 33 is saturated at all times with the acid solution in the anodechamber 17.

In the construction of the unit 10, it will be understood that afterremoval of the fitting 49 from the tubular member 48, the anode 12,together with the sleeve 29, may be withdrawn from the upper end of thefitting 44- for adjustment, repair or replacement, as required. When thevalve 56 occupies its open position, a controlled flow of water into thetubular member 47 is efiected by the flow control plug 54 and thencedownwardly through the anode chamber 17 and from the tubular member 40and thus upwardly through the conduit structure fill to the exterior;and similarly, when the valve 59 occupies its open position, water flowsthrough the conduit 57 upwardly through the cathode chamber 16 and outof the conduit 58. Accordingly, the stream of water flowing downwardlythrough the anode chamber 17 is in counterflow with respect to thestream of water flowing upwardly through the cathode chamber 16. Thestream of water flowing through the anode chamber 17 readily penetratesthe porous ion exchange bed 33 therein and is in wetting relationtherewith and with the barrier 13, as well as the anode 12 by virtue ofthe perforations 31 provided in the insulating sleeve Zfi. Similarly,the stream of water flowing through the cathode chamber 16 is in wettingrelation with the barrier 15 and the cathode ll. As explained more fullyhereinafter, the stream of water flowing through the anode chamber 17constitutes an anolyte that is an aqueous acid solution, while thestream of water flowing through the cathode chamber 15 constitutes acatholyte that is an aqueous base solution.

The elements 44, etc., are also connected to ground potential; wherebythe ungrounded anode 12 is completely electrically insulated from thegrounded cathode ll and from the elements 44, etc.; whereby theapplication of positive potential between the anode l2 and the cathodell effects an electrolytic action upon the two streams of waterrespectively traversing the chambers 16 and 17 and upon the ion exchangebed 33.

Turning now to the composition of the ion exchange bed 33, it preferablycomprises a mixed bed of discrete particles of cation exchange materialand discrete particles of anion exchange material, although it maycomprise only discrete particles of cation exchange material.Specifically, it is preferable that the porous bed 33 comprises firstdiscrete particles of a synthetic organic polymeric cation exchangeresin and second discrete particles of a synthetic organic polymericanion exchange resin, the two types of particles being heterogeneouslymixed (about 50%50% by volume) in the mass of the bed 33, therebyproducing approximately equal cation exchange and anion exchangecapacities.

More particularly, this cation exchange resin is of bead-like formationand may comprise the strong-acid resin sold by Rohm and Haas under thename Amberlite lR-lZO, and this anion exchange resin is of headlikeformation and may comprise the strong-base resin sold by Rhom and Haasunder the names Amberlite IRA-400 and Amberlite IRA-410. A cationexchange resin of the type specified essentially comprises a stableinsoluble synthetic organic polymer, active acidic functional groupschemically bonded thereto and dissociable into free mobile cations toimpart a negative charge to the polymer, and Water in gel relationshipwith the polymer. Similarly, an anion exchange resin of the typespecified essentially comprises a stable insoluble synthetic organicpolymer, active basic functional groups chemically bonded thereto anddissociable into free mobil anions to impart a positive charge to thepolymer, and water in gel relationship with the polymer. The activeacidic functional groups attached to the associated organic polymer areoriented with respect to the interfaces thereof so as to be partially orcompletely dissociable in the internal gel water into fixed negativeions linked to the polymer and into mobile exchangeable positive ions;andv similarly, the active basic functional groups attached to theassociated organic polymer are oriented with respect to the interfacesthereof so as to be partially or completely dissociable in the internalgel water into fixed positive ions linked to the polymer and into mobileexchangeable negative ions.

animate Typical such polymers to which active acidic func- 'tionalgreups may be attached include: phenol-aldehyde resins,polystyrene-divinylbenzene copolymers, and the like; and s'uchsuit'ableactive acidic functional groups include: -S O H, -COOH and the like; SOH being preferred because of its high dissociation constant. Typicalsuch polymers to which active basic functional groups may be attachedinclude: urea-formaldehyde resins, melamine-formaldehyde resins,polyalkylene-polyairline-formaldehyde resins, and the like; and suchsuitable active basic functional groups include: quaternary ainmeniumhydroxides, amino groups, the guanidyl group, the dicyanodiamidinegroup, and like organic nitrogen-containing basic groups, the quaternaryammonium hydroxide groups, thequar'iidine and the dicyanodiamidineresidue beingusuallypreferred because of their dissociation constants.Normally the water in gel relationship with the polymer should bepresent in an amount ofat least 15% of the weight of the dry resin. a Asa constructional example of the unit 10, especially designed for use indishwashing apparatus of the home appliance type, the internal diameterof the cathode 11 be 37s"; the internal diameter of the barrier 13 maybeZ /i"; the diameter of the anode may be the distance between theadjacent upper and lower surfaces of the plates 18 and 19 may be 6%";the other dimensions are appropriately related; and the volume of thebed 33 may be 0.02 cuhicfoot. 7

his contemplated that this constructional example of the unit 10 will beincorporated in dishwashing apparatus, as disclosed in thepreviously-mentioned Stoddard application; wherebythe water is conductedthrough the anode compartment 17 in a single demand and involving a timeinterval of about 30 seconds; whereby the flow control plug 54 may beconstructed and arranged to accommo date the passage therethrough ofthree gallons per minute, thereby accommodating the passage of sixquarts of anolyte through the anode chamber 17 in each cycle ofoperation of the dishwashing apparatus mentioned. On the other hand, theflow of the catholyte through the cathode compartment 16 may becontinuous and at the exceedingly low rate of about 12 gallons permonth. In this case, the direct current may be conducted from the anode12 to the cathode 31 continuously at about 0.1 ampere by impressing adirect voltage between the anode 12 and the cathode 11 of about 7-volts;whereby the energy requirement ofthe unit 10 may have an average valueof about 0.5 kilowatt-hour per month, this value being somewhat variableand dependent upon the character of the hard water being treated.

Turning now more particularly to the treatment of water in the unit 10,it is first noted that ordinary hard water contains dissolved metalsalts, particularly salts of alkali earth metals, which electrolytesinclude such cations as: Card", Mgr- Na FeH, etc., and such anions as:Cl-, HCO CO; 3804- N etc. Hard Water to be treated frequently contains adissolved solids count of 250 p.p.m. and higher, comprising dissolvelelectrolytes yielding the cations and the anions named; whereby itistotally unsuitable for use in the dishwashing apparatus mentioned forseveral reasons. In the first place, certainof thesecations-particularly Ca++ form precipitates with lordinary detergentsand also with many food s'oils, introduced into the dishwasher on thedishes; whereby the resulting solids are'deposited upon the dishesproducing undesirable films, stains, etc. Moreover, incident to dryingof the dishes, the evaporation of the water films thereon causes thedeposit of metal salts thereon, as it is apparent that when the solventis evaporated the concentration of the cations and anions thereinexceeds the solubility of the corresponding salts; whereby GaCO forexample, is deposited upon the dishes producing corresponding scalethereon. Now in the practical demineralization of hard water, it is notneces sary to remove all of the dissolved solids but only to 6 reducethe total dissolved solids to a tolerable valu. For example, Chicagocity water isonly moderately hard containing about p.p.m. of hardnessions (calculated as CaCO and can be rendered altogether soft from apractical standpoint, by reducing the content of these hardness ions to35 p.p.m. Restating the matter in terms of grains of hardness, Chicagocity water is of 8 grains hardness; whereby the volume of the ionexchange bed 33 has a capacity for softening 87.5 gallons of Chicagocity water, since this volume of the bed 34 has an absolute capacity ofreacting with 700 grains of water hardness. Now during the long timeinterval when no anolyte is conducted through the anode compartment 17,the continuous passage of the direct electric current between the anode12 and the cathode 11 effects regeneration of the resin incorporated inthe bed 33, and it may be readily calculated that this regeneration isat least 10% of that of the total capacity of the bed 33; whereby it isapparent that the unit 10 is regenerated to accommodate the softening of8.75 gallons of Chicago city water per day. Now even if the dishwashingapparatus mentioned were installed in an area having exceedingly hardwater, such, for example, as a few areas having a water hardness as highas 25 grains, the regeneration capacity of the unit 10 is then reducedto only 2.9 gallons per day. However, the conduction of even this volumeof anolyte through the anode chamber 17 of the unit 10 is not requiredin the cycle of the dishwashing apparatus mentioned. g i

In the above discussion, only the demineralization or softening of hardwater has been referred to, birth will be understood that theelectrolysis that proceeds in the unit 10 is effective moderately toreduce the pH of the anolyte and substantially to increase the pH of thecatholyte; whereby the reduction in the pH of the anolyte serves anothervery important function in the operation of the dishwashing apparatusmentioned in that the rinse water involved in the automatic cyclethereof, being thoroughly acidified, is capable of dissolving previouslydeposited metal salts from the dishes undergoing the dishwashingoperation, as it is apparent that the solubility of the metal salts issubstantially increased as thepH of V the final rinse solution isreduced with respect to neutral ity. Thus this effect that is achievedin the dishwashing apparatus mentioned is most beneficial in obtaining asatisfactory appearance of the dishes at the conclusion of the washingcycle.

The foregoing considerations Will be understood in conjunction with abrief description of the electrodialysis that occurs in the unit 10.More particularly, the cations of the electrolytes dissolved in theanolyte are transported by diffusion through the permeable barrier 13into the catholyte by virtue of the attraction between the positiveelectrical charges and the cathode 11; and conversely, the anions of theelectrolytes dissolved in the catholyte are transported by diffusionthrough the permeable barrier 13 into the anolyte by virtue of theattraction between the negative electrical charges and the anode 12.Thus the cations are preferentially extracted from the anolyte andaccumulated in the catholyte, and the anions are preferentiallyextracted from the catholyte and accumulated in the anolyte. Of course,the extraction of cations from the anolyte, as well as the accumulationof anions therein, effects an increase in the hydrogen ion concentrationin the anolyte; whereby the pH of this aqueous solution iscorrespondingly reduced and may be disposed Within the range 4.0 to 5.0,in the operation of the unit 10; and conversely, the extraction of theanions from the catholyte, as Well as the accumulation of cationstherein, effects a decrease in the hydrogen ion concentration in thecatholyte; whereby the pH of this aqueous solution iscorrespondinglyincreased and may be disposed within the range 9.0 to 10.0, in theoperationof the unit -10. Of course, some oxygen is evolved at the anode12 that is swept along with the anolyte Z through the tubular member 40;while some hydrogen is evolved at the cathode 11 that is swept alongwith the catholyte through the conduit 58.

During the conduction of the water through the bed 33 substantialamounts of the cations and the anions of the electrolytes dissolved inthe raw water are respectively exchanged with hydrogen ions and hydroxylions respectively by the cation exchange resin particles and by theanion exchange resin particles, thereby correspondingly depletingrespectively the cation exchange capacity of the cation exchange resinparticles and the anion exchange capacity of the anion exchange resinparticles. However, when the valve 56 in the supply pipe communicatingwith the anode compartment 17 is subsequently closed, the cationexchange resin particles and the anion exchange resin particles undergopartial regeneration, since the conduction of the direct current fromthe anode 12 to the cathode 11 is continuous. Specifically, the cationexchange resin particles are regenerated by the release of the cationsof the previously exchanged metal salts and by the recapture of hydrogenions from the anolyte, which cations diffuse through the permeablebarrier 13 into the continuously flowing catholyte and are transportedto the exterior of the unit 10, as previously explained. Similarly, theanion exchange resin particles are regenerated by the release of theanions of the previously exchanged metal salts and by the recapture ofhydroxyl ions from the anolyte, which anions accumulate in the anolytewith the ultimate formation of oxygen molecules dispersed therethrough.

The arrangement of the mixed resin bed 33 in the anode chamber 17 isvery advantageous as it materially reduces the internal resistance ofthe unit between the anode 12 and the cathode 11 greatly facilitatingthe migration of both the cations and the anions through the permeablebarrier 13, whereby the heating of the anolyte and the catholyte passingthrough the unit 10 is greatly minimized; thereby drastically reducingthe energy re quirements thereof. Although the phenomenon is notaltogether understood, it is surmised that the resins in the mixed resinbed 33 constitute solid poly-electrolytes for the transportation of theions; and specifically, it is visualized that the cations are involvedin a great multiplicity of exchanges with a considerable number of theindividual cation exchange particles in their migration toward thecathode 11, and that the anions are involved in a great multiplicity ofexchanges with a considerable number of the individual anion exchangeparticles in their migration toward the anode 12; the mechanism involvedbeing visualized as like the mode employed in playing the childs game ofmusical chairs. In this mechanism, it is suggested that the energyrequired to effect the successive ion exchanges of a great number of theions in the mixed resin bed 33 and the consequent transportation of agreat number of the ions between the anolyte and the catholyte is verysmall compared to the energy required to effect the direct migration ofthe same given number of ions through the same distance in the anolyteor in the catholyte, due fundamentally to the fact that in the directmigration of the ions there must be a great amount of energy lostthrough random collision by the ions with water molecules and the ionsmust expend a great amount of work upon these dipolar molecules inpassing therethrough. In any case, and without reference to the exactmechanism involved, the utilization of the mixed resin bed 33 in theanode chamber 17 drastically reduces the energy requirements of the unit10 with respect to the requirements thereof in the absence of the mixedresin bed 33 to effect the same total ion exchange. Moreover, theprovision of the mixed resin bed 33 permits a substantial reduction inthe size of the unit 10 as it in effect permits of the accumulation orstorage of ion exchange capacity during the extremely long time intervalduring which the anolyte is not actively conducted through the anodecompartment 17. In this connection, it is noted that-the continuousconduction of the catholyte through the cathode chamber 16 is veryimportant as the arrangement insures that the ion exchange bed 33remains wet at all times and in readiness to effect the required ionexchange when the anolyte is conducted through the anode chamber 17during the short time interval, as it will be recalled that in thesepolymeric ion exchange resins water must be maintained in gelrelationship with respect thereto, as the ion exchange mechanism thereofinvolves the utilization of this water in gel relationship therewith. Inother words, it is important that the ion exchange bed 33 be floodedwith water at all times so that it is in readiness to perform therequired ion exchange function at all times.

Recapitulating, in conjunction with the operation of the unit 10: theraw Chicago city water in the supply pipe connected to the member 47 maycontain 8 grains of hardness and have a pH of 7.0; whereas the anolytethat is conducted through the anode chamber 17 and employed in theautomatic cycle of the dishwashing apparatus mentioned may contain about2 grains of hardness and have a pH within the approximate range 4.0 to5.0. In passing, it is noted that the catholyte that is conductedthrough the cathode chamber 16 is flushed into the drain plumbing of thedishwashing apparatus mentioned, as such is useful to bring about thesaponifi cation of the higher fatty acids of animal and vegetable originthat tend to collect and cake therein, since the catholyte has a pH wellin the base range, as previously noted. The raw water that is suppliedinto the anode chamber 17 may have a pressure of about 25 p.s.i., andthe flow control plug 54 accommodates the flow through the anode chamber17 at a rate of about 12 quarts per minute; while the raw water that issupplied via the valve 59 into the cathode chamber 16 flows at anexceedingly small rate of about 12 gallons per month. Accordingly, thetotal quantities and the flow rates of the water through the respectivecathode chamber 16 and the anode chamber 17 are altogetherdisproportional in the normal operation of the dishwashing apparatusmentioned. Specifically, the catholyte is conducted continuously throughthe cathode chamber 16 in a total quantity of about 12 gallons in aperiod of 1 month or 30 days; whereas the anolyte is conductedintermittently through the anode chamber 17 about once per day or 30times per month and in the total quantity of about gallons in the periodof 1 month or 30 days. Thus the conduction of the catholyte through thecathode chamber 16 is at a rate of about 2.8 10 gallons per minute,while the conduction of the anolyte through the anode chamber 17 is at arate of about 3.0 gallons per minute; whereby the rate of flow of theanolyte through the anode chamber 17 is about 10,000 times as great asthe rate of flow of the catholyte through the cathode chamber 16.However, the arrangement is entirely feasible, since the flow of theanolyte at its relatively high rate through the anode chamber 17 occursonly for about 1 minute in each twenty-four hour period; whereas theflow of the catholyte at its exceedingly low rate through the cathodechamber 16 occurs continuously; the ion exchange bed 33 has a high rateof expenditure of its accumulated capacity to exchange ions; and the ionexchange bed 33 is under continuous regeneration at the low rateinvolving the continuous conduction therethrough of the direct electriccurrent of about 0.1 amp. 7

Finally, it is pointed out in conjunction with the operation of the unit10 that it may be arranged either preceding or following a hot waterheater, whereby the raw water supplied thereto may be the ambienttemperature of about 50 F., or the elevated temperature of about F. inthe respective locations noted.

While the construction and utilization of the unit 10 have beendescribed in conjunction with dishwashing apparatus, because of thedivisional character of the present application, it will be understoodthat it is of general utility for the production from ordinary hardWater of separate and distinct aqueous acid and base solutions of thecharacter specified, that may be employed for other purposes.

The construction and arrangement of the unit is disclosed and claimed inthe copending combination divisional and continuation-impart applicationof Edgar S. Stoddard, Serial No. 734,971, filed May 13, 1958.

In view of the foregoing, it is apparent that there has been provided animproved method of producing separate and distinct aqueous acid and basesolutions from ordinary hard water, that is particularly useful inconjunction with dishwashing apparatus, or the like.

While there has been described what is at present considered to be thepreferred embodiment of the invention, it will be understood thatvarious modifications may be made therein, and it is intended to coverin the appended claims all such modifications as fall within the truespirit and scope of the invention,

What is claimed is:

1. The method of treating raw water containing small amounts ofdissolved metal salts in an electrolytic cell comprising a permeablediaphragm defining a cathode chamber and an anode chamber on oppositesides thereof and including a mixed ion exchange bed in said anodechamber; said method comprising: (1) conducting continuously during atime interval T a small quantity Q1 of said raw water at a relativelylow rate of flow R1 through said cathode chamber into wetting relationwith said diaphragm; (2) conducting intermittently during said timeinterval T a large quantity Q2 of said raw water at a relatively highrate of flow R2 through said anode chamber into wetting relation withsaid diaphragm and into ion exchange relation with said bed; and (3)conducting continuously during said time interval T a direct electriccurrent from the water in said anode chamber into the water in saidcathode chamber and through said bed and said diaphragm, whereby twoaqueous solutions S1 and S2 respectively result from said two quantitiesQ1 and Q2 of said raw water, and whereby the proportions of the cationsand anions of said metal salts in said two solutions S1 and S2 aresubstantially modified respectively in reverse directions with respectto that in said raw water.

2. The method set forth in claim 1, wherein the ratio between the ratesR1/R2 1/ 1000.

3. The method set forth in claim 1, wherein said bed comprises a looselypacked mass of first discrete particles of cation exchange material andof second discrete particles of anion exchange material.

4. The method set forth in claim 3, wherein said cation exchangematerial consists essentially of synthetic organic polymeric cationexchange resin and said anion exchange material consists essentially ofsynthetic organic polymeric anion exchange resin.

5. The method set forth in claim 1, wherein said solution S1 constitutesa catholyte having a pH above 7.0 and 10 said solution S2 constitutes ananolyte having a pH below 7.0.

6. The method of treating raw water containing small amounts ofdissolved metal salts in an electrolytic cell comprising a permeablediaphragm defining a cathode chamber provided with a cathode and ananode chamber provided with an anode and including a mixed ion exchangebed in said anode chamber; said method comprising: (1) continuouslyconducting a first stream of said raw water at a relatively low rate offlow through said cathode chamber into wetting relation with one side ofsaid diaphragm and with said cathode; (2) intermittently conducting asecond stream of said raw water at a relatively high rate of flowthrough said anode chamber into wetting relation with the other side ofsaid diaphragm and with said anode and into ion exchange relation withsaid bed; and (3) continuously conducting a direct electric current fromsaid anode to said cathode and through said bed and said diaphragm andthrough said first and second streams of said raw water, whereby firstand second streams of aqueous solutions respectively result from saidfirst and second streams of said raw water, and whereby the proportionsof the cations and the anions of said metal salts in said first andsecond streams of aqueous solutions are substantially modifiedrespectively in reverse directions with respect to that in said rawwater, so that said first stream of aqueous solution has a pHsubstantially higher than that of said raw water and said second streamof aqueous solution has a pH substantially lower than that of said rawwater.

7. The method set forth in claim 6, wherein the cation exchange materialin said bed consists essentially of synthetic organic polymeric cationexchange resin, and the anion exchange material in said bed consistsessentially of synthetic organic polymeric anion exchange resin.

8. The method set forth in claim *6, wherein the temperature of the rawwater in the first and second streams respectively conducted throughsaid first and second chambers is well below F.

9. The method set forth in claim 6, wherein the temperature of the rawwater in the first and second streams respectively conducted throughsaid first and second chambers is well above 100 F.

References Cited in the file of this patent UNITED STATES PATENTS2,502,614 Zender Apr. 4, 1950 2,546,254 Briggs Mar. 27, 1951 2,681,885Briggs June 22, 1954 2,741,591 Dewey et al. Apr. 10, 1956 2,763,607Staverman Sept. 18, 1956 FOREIGN PATENTS 1,066,583 France Jan. 20, 1954OTHER REFERENCES Industrial and Engineering Chemistry, vol. 47, No. 1,January 1955, pp. 61 to 67, by Walters et al.

1. THE METHOD OF TREATING RAW WATER CONTAINING SMALL AMOUNTS OF DISSOLVED METAL SALTS IN AN ELECTROLYTIC CELL COMPRISING A PERMEABLE DIAPHRAGM DEFINING A CATHODE CHAMBER AND AN ANODE CHAMBER ON OPPOSITE SIDES THEREOF AND INCLUDING A MIXED ION EXCHANGE BED IN SAID ANODE CHAMBER, SAID METHOD COMPRISING (1) CONDUCING CONTINUOUSLY DURING A TIME INTERVAL T A SMALL QUANTITY Q1 OF SAID RAW WATER AT A RELATIVELY LOW RATE OF FLOW R1 THROUGH SAID CATHODE CHAMBER INTO WETTING RELATION WITH SAID DIAPHRAGM; (2) CONDUCTING INTERMITTENTLY DURING SAID TIME INTERVAL T A LARGE A QUANTITY Q2 OF SAID RAW WATER AT A RELATIVELY HIGH RATE OF FLOW R2 THROUGH SAID ANODE CHAMBER INTO WETTING RELATIONWITH SAID DIAPHRAGM AND INTO ION EXCHANGE RELATION WITHSAID BED; AND (3) CONDUCTING CONTINUOUSLY DURING SAID TIME INTERVAL T A DIRECT ELECTRIC CURRENT FROM THE WATER IN SAID ANODE CHAMBER INTO THE WATER IN SAID CATHODE CHAMBER AND THROUGH SAID BED AND SAID DIAPHRAGM, WHEREBY TWO AQUEOUS SOLUTIONS S1 AND S2 RESPECTIVELY RESULT FROM SAID TWO QUANTITIES Q1 AND Q2 OF SAID RAW WATER, AND WHEREBY THE PROPORTIONS OF THE CATIONS AND ANIONS OF SAID METAL SALTS IN SAID TWO SOLUTIONS S1 AND S2 ARE SUBSTANTIALLY MODIFIED RESPECTIVELY IN REVERSE DIRECTIONS WITH RESPECT TO THAT IN SAID RAW WATER. 